kvm: Remove ept_identity_pagetable from struct kvm_arch.

kvm_arch->ept_identity_pagetable holds the ept identity pagetable page. But
it is never used to refer to the page at all.

In vcpu initialization, it indicates two things:
1. indicates if ept page is allocated
2. indicates if a memory slot for identity page is initialized

Actually, kvm_arch->ept_identity_pagetable_done is enough to tell if the ept
identity pagetable is initialized. So we can remove ept_identity_pagetable.

NOTE: In the original code, ept identity pagetable page is pinned in memroy.
      As a result, it cannot be migrated/hot-removed. After this patch, since
      kvm_arch->ept_identity_pagetable is removed, ept identity pagetable page
      is no longer pinned in memory. And it can be migrated/hot-removed.

Signed-off-by: Tang Chen <tangchen@cn.fujitsu.com>
Reviewed-by: Gleb Natapov <gleb@kernel.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

3 files changed, 22 insertions, 28 deletions

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 2dbde3b7446c..028df8dc538e 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -578,7 +578,6 @@ struct kvm_arch {
 
         gpa_t wall_clock;
 
-        struct page *ept_identity_pagetable;
         bool ept_identity_pagetable_done;
         gpa_t ept_identity_map_addr;
 
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 5db47db6574b..5de0d7b1d8a9 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -767,6 +767,7 @@ static u32 vmx_segment_access_rights(struct kvm_segment *var);
 static void vmx_sync_pir_to_irr_dummy(struct kvm_vcpu *vcpu);
 static void copy_vmcs12_to_shadow(struct vcpu_vmx *vmx);
 static void copy_shadow_to_vmcs12(struct vcpu_vmx *vmx);
+static int alloc_identity_pagetable(struct kvm *kvm);
 
 static DEFINE_PER_CPU(struct vmcs *, vmxarea);
 static DEFINE_PER_CPU(struct vmcs *, current_vmcs);
@@ -3962,21 +3963,27 @@ out:
 
 static int init_rmode_identity_map(struct kvm *kvm)
 {
-        int i, idx, r, ret;
+        int i, idx, r, ret = 0;
         pfn_t identity_map_pfn;
         u32 tmp;
 
         if (!enable_ept)
                 return 1;
-        if (unlikely(!kvm->arch.ept_identity_pagetable)) {
-                printk(KERN_ERR "EPT: identity-mapping pagetable "
-                        "haven't been allocated!\n");
-                return 0;
+
+        /* Protect kvm->arch.ept_identity_pagetable_done. */
+        mutex_lock(&kvm->slots_lock);
+
+        if (likely(kvm->arch.ept_identity_pagetable_done)) {
+                ret = 1;
+                goto out2;
         }
-        if (likely(kvm->arch.ept_identity_pagetable_done))
-                return 1;
-        ret = 0;
+
         identity_map_pfn = kvm->arch.ept_identity_map_addr >> PAGE_SHIFT;
+
+        r = alloc_identity_pagetable(kvm);
+        if (r)
+                goto out2;
+
         idx = srcu_read_lock(&kvm->srcu);
         r = kvm_clear_guest_page(kvm, identity_map_pfn, 0, PAGE_SIZE);
         if (r < 0)
@@ -3994,6 +4001,9 @@ static int init_rmode_identity_map(struct kvm *kvm)
         ret = 1;
 out:
         srcu_read_unlock(&kvm->srcu, idx);
+
+out2:
+        mutex_unlock(&kvm->slots_lock);
         return ret;
 }
 
@@ -4043,31 +4053,20 @@ out:
 
 static int alloc_identity_pagetable(struct kvm *kvm)
 {
-        struct page *page;
+        /* Called with kvm->slots_lock held. */
+
         struct kvm_userspace_memory_region kvm_userspace_mem;
         int r = 0;
 
-        mutex_lock(&kvm->slots_lock);
-        if (kvm->arch.ept_identity_pagetable)
-                goto out;
+        BUG_ON(kvm->arch.ept_identity_pagetable_done);
+
         kvm_userspace_mem.slot = IDENTITY_PAGETABLE_PRIVATE_MEMSLOT;
         kvm_userspace_mem.flags = 0;
         kvm_userspace_mem.guest_phys_addr =
                 kvm->arch.ept_identity_map_addr;
         kvm_userspace_mem.memory_size = PAGE_SIZE;
         r = __kvm_set_memory_region(kvm, &kvm_userspace_mem);
-        if (r)
-                goto out;
-
-        page = gfn_to_page(kvm, kvm->arch.ept_identity_map_addr >> PAGE_SHIFT);
-        if (is_error_page(page)) {
-                r = -EFAULT;
-                goto out;
-        }
 
-        kvm->arch.ept_identity_pagetable = page;
-out:
-        mutex_unlock(&kvm->slots_lock);
         return r;
 }
 
@@ -7758,8 +7757,6 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id)
                         kvm->arch.ept_identity_map_addr =
                                 VMX_EPT_IDENTITY_PAGETABLE_ADDR;
                 err = -ENOMEM;
-                if (alloc_identity_pagetable(kvm) != 0)
-                        goto free_vmcs;
                 if (!init_rmode_identity_map(kvm))
                         goto free_vmcs;
         }
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 68660b31457e..2d7f65daa8d0 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7273,8 +7273,6 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
         kvm_free_vcpus(kvm);
         if (kvm->arch.apic_access_page)
                 put_page(kvm->arch.apic_access_page);
-        if (kvm->arch.ept_identity_pagetable)
-                put_page(kvm->arch.ept_identity_pagetable);
         kfree(rcu_dereference_check(kvm->arch.apic_map, 1));
 }